Brake problem

[ari]

Just fitted some secondhand rear brakes , the lever feels solid but needs to be pumped once to get braking happening[bled it 100 times , no air definitely ] , the thing is the caliper is a 4 pot and master cylinder is from a 2 pot system, so , is there differences with the 4 and 2 systems??[asking for a friend if its a noob question]

 

[Astro66]

Yes. Volume of oil. A 4 pot caliper needs more oil pumped.

 

[Anders]

The thing is the caliper is a 4 pot and master cylinder is from a 2 pot system, so , is there differences with the 4 and 2 systems??[asking for a friend if its a noob question]

I think your friend has the answer right there

As a general rule, I would say that a 4-pot caliper has a bigger piston area, hence need more oil volume to move the pistons the necessary distance.
That would generally need a bigger piston in a 4-pot mastee than in a 2-pot master. If your master cylinder's piston is too small, I guess you would get the behavior that you describe.

 

[VWsurfbum]

it could just be that the pads are worn, the pistons need to be eased out. could be that there's not enough fluid, so it will create a vacuum to suck the pistons back, so maybe take the master cylinder plug out and put your syringe in or pot whatever you use to bleed in. Then pump the pistons out.
Another way to do it is to strap the leaver to the bars (close to) once the pads have connected to the disc and leave for a few hours. (again I do this while I have the pot in the leaver)

 

[ari]

it could just be that the pads are worn, the pistons need to be eased out. could be that there's not enough fluid, so it will create a vacuum to suck the pistons back, so maybe take the master cylinder plug out and put your syringe in or pot whatever you use to bleed in. Then pump the pistons out.
Another way to do it is to strap the leaver to the bars (close to) once the pads have connected to the disc and leave for a few hours. (again I do this while I have the pot in the leaver)

I'll give that a go , thanks.